This invention relates to a magnetic disk apparatus utilizing removable disk means and fixed disk means.
A magnetic disk apparatus is widely used as a bulk memory in a data-processing system. In a magnetic disk apparatus utilizing both removable and fixed disk means, the fixed disk means is permanently seated on a drive spindle rotatably supported on a base casting. On the other hand, the removable disk means enclosed in a disk cartridge is interchangeably mounted on the upper end portion of the drive spindle. A first group of magnetic heads cooperating with the fixed disk means and a second group of magnetic heads cooperating with the removable disk means are fitted to a common head positioning device. Accordingly, the magnetic heads are shifted from track to track along the surface of the corresponding disk means. The above-mentioned elements are received in a housing provided with a door through which the disk cartridge passes.
One of the greatest problems of the prior art magnetic disk apparatus constructed as described above is that considerable difficulties are encountered in carrying out the maintenance of the fixed disk means and the magnetic heads cooperating therewith. The reason for this is that the fixed disk means is permanently set on the inner bottom space of a housing defying an easy access by a maintenance operator.
Another drawback of the conventional magnetic disk apparatus is that while recording or readout is carried on with respect to a particular track formed in either the fixed or the removable disk means, it is impossible to undertake recording or readout with respect to a different track on the other disk means. The reason for this is that the first group of magnetic heads cooperating with the fixed disk means and the second group of magnetic heads cooperating with the removable disk means are fitted to a common head-positioning device, making it impossible to independently control the positions of the first and second groups of magnetic heads.
Further problem of the known magnetic disk apparatus is that recording or readout can not be effected with respect to the fixed disk means, unless the removable disk means is mounted on the drive spindle. The reason for this is that while the removable disk means is not mounted on the drive spindle, the first group of magnetic heads cooperating with the fixed disk means and the second group of magnetic heads cooperating with the removable disk means have to be held in a retracted position alike.